It is no exaggeration that miniaturization of a semiconductor integrated circuit pattern has been accomplished due to the progress of photolithography and peripheral techniques thereof. This photolithography includes two main generally known techniques. One is a technique on an exposure wavelength or a numerical aperture of a reduction projection exposure apparatus known as a stepper or a scanner. The other is a technique on resist properties such as printing resolution of a photoresist composition in which a mask pattern is printed by the aforementioned reduction projection exposure apparatus. These are interacted with each other like two wheels of a car, thereby improving processing accuracy of a semiconductor integrated circuit pattern by means of photolithography.
The wavelength of light sources used in the reduction projection exposure apparatus has been increasingly shortened in response to a demand for high resolution circuit patterns. In general, the g-line (436 nm) or i-line (365 nm) of a mercury lamp is used in the case of a resist resolution of about 0.5 μm or 0.30 to about 0.5 μm, respectively. The main spectra of the g-line and i-line are 436 nm and 365 nm, respectively. Also, a KrF excimer laser (248 nm) or an ArF excimer laser (193 nm) is used in the case of a resist resolution of 0.15 to about 0.30 μm, or about 0.15 μm or less, respectively. Furthermore, use of an F2 excimer laser (157 nm), an Ar2 excimer laser (126 nm), and EUV (extreme ultraviolet light, wavelength: 13 nm) is being investigated in order to further miniaturize a semiconductor integrated circuit pattern.
As far as a photoresist composition is concerned, the life of a photoresist for KrF in lithography using a KrF excimer laser is currently prolonged by combining this photoresist with an organic or inorganic anti-reflective film or by devising an exposure system, and the photoresist composition with an eye to about 110 nm, which is below λ/2, is being developed. Also, provision of a photoresist composition for ArF has been desired, which is preferable for the mass production of a prospective fine pattern with a node of about 90 nm or less in lithography using an ArF excimer laser. Furthermore, lithography using the aforementioned F2 excimer laser has drawn attention as a technique for processing a prospective fine pattern with a node of 65 nm or less, and a photoresist composition is being developed which is applicable to fine processing by lithography using an F2 excimer laser.
Since it is difficult for a conventional positive photoresist including an alkali soluble novolak resin and a quinone diazide group-containing compound as main components to achieve such a fine pattern, a photoresist applicable to a far-UV ray with a further shortened wavelength (200 to 300 nm); an excimer laser such as KrF, ArF, or F2; an electron beam; and X ray has been desired to be developed. As such a photoresist, a chemically amplified resist has drawn attention and is being actively developed, in which a catalytic reaction and a chain reaction due to acid generated on exposure to radiation can be realized, the quantum yield is 1 or higher, and high resolution and sensitivity can be achieved.
Examples of the chemically amplified resist include a photoresist containing an acetal group, a tertiary alkyl group such as a tert-butyl group, tert-butoxycarbonyl group, or tert-butoxycarbonylmethyl group as an acid dissociable protecting group of a fluorinated alcohol as disclosed in the following non-patent references 1 to 3.
However, in these chemically amplified resists disclosed in non-patent references 1 to 3, the resolution and shape of a resist pattern are not sufficient, and further improvement has been desired.
[Non-Patent Reference 1]
T. Hagiwara, S. Irie, T. Itani, Y. Kawaguchi, O. Yokokoji, S. Kodama, J. Photopolym. Sci. Technol. Vol. 16, Page 557, 2003.
[Non-Patent Reference 2]
F. Houlihan, A. Romano, D. Rentkiewicz, R. Sakamuri, R. R. Dammel, W. Conley, G. Rich, D. Miller, L. Rhodes, J. McDaniels, C. Chang, J. Photopolym. Sci. Technol. Vol. 16, Page 581, 2003.
[Non-Patent Reference 3]
Y. Kawaguchi, J. Irie, S. Kodama, S. Okada, Y. Takebe, I. Kaneko, O. Yokokoji, S. Ishikawa, S. Irie, T. Hagiwara, T. Itani, Proc. SPIE, Vol. 5039, Page 43, 2003.